Protectors for electric circuits



' Marci: 31, 1959 F. BUSSMANN PROTECTORS FOR ELECTRIC CIRCUITS FiledJan. 14, 1955 O 2 6 32 8 4 9 2 4 5 3 2 3 6 E O m 0 O m 8 6 5 7/ 8 6 L:O4 6 4 5 5 m M 4 m 0 8 5 7 4 6 y 6 II 0 6 7 2 3 2 9% a 3 M 2 l flflw |NVENTOR.

H Bussnnmv ATTORNEY FRANK eshares. P n

PROTECTORS FOR ELEoTRro GIRGUITS Frank H. Bussmann, .Qlayton, Mo-,..:assignor to McGraw- Edison Company, a. col mation ofv DelawareApplication January 14, 1955 Serial No. 481,776 7 Cl ms ((1 acumenaction" in opening the circnit, That snapeaction istend t s p rat the,s'wil Q l Qn actfiifiO rapidly'that rc n o fo m; or if! arcsShQUidifQl'IIl, to lengthen:

those arcs so rapidly: that they, cannot. bev maintained ut m st xt ngush hems lves.

While a snap-action? of the. switch contacts is de.-

sirable in circuit-opening operations on direct current.

installations, a less-rapid action oh the. switch; contacts;

is desirable in circuit-opening operations on alternating currentinstallations, A very 'gapid, opening of the. switch n c su h a sexperienced. in. a snap-action?" Cir: p n n op ation. could. be. startedand mp during either of the hi hivoltage: portions of a. currentv cycle,and there would, thenea. strong, tendency toward.

arcing However, a. less-rapid openingQitheswitch con.-

tacts would consume an an onnt of, tirne -that. would 611% able thevoltage to; drop toward; t ezeIo-value; beforev the circuit-openingoperation wasg completed; :anththere would en b a g yessened tendencytewardarcin The.

present invention. utilizes; his mPQttant: principles to provideaself-contained n anuallyeopcrtble.electric switch.

F I e ab y. and: les @0 1: than has; heretofore been p s le. It s hrefore an: obj ct of the; res nt invention to provide. a selt-contained,mannallyeoperablcz le tric switchthat hasarelatively sl wireuit-breakng:

action.

The presentinventionhas a movable Contact and a fix d n and h sahandlethat,is.mQY b e..to.-e us movement of the movable contactThathanclle, 1S,II1OY:--

able to an on position and to an ofi position; and it has a high pointthat moves througha dead center posi tion as the handle moves from theon position to the off position. Thathighpointmoves the movablecontactaway from the'fixed contact to open the circuityand when thathighpoint is in thedead center position'it" will hold the movable contact-aconsiderable distance away from the fixed. contact;

close-together, when the handles were. be dead; cen, ter. position,arcing could occur, However; byhaving the high Point. of h h ndl h d:.t.:mo able:contact; at

consid ra stanc away f onr hefixed cntactgwhen-a e e h h po nt isuin theead e nteruce tionathe cause fires.v To pres This is very desirablesince the handles of: switches can sometimes, through in-.-- ti n or nav rt nee. H,.thiP3fiTQfi-I the; operator, be. s n. th de c nte Po ti n;a d.itrtheccnta tsrwere-.

present invention avoids any such arcing. It is therefore an object ofthe present invention to provide a switch with a movable contact and afixed contact and with a handle that has a high point to hold thecontacts apart a considerable .distance whenever said handle is in thedead center position.

The movable contact of the. switch provided by the present invention isacantilever plate. That movable contact is biased toward a fixed contactby a helical compression spring. That spring is strong, :and it urgesthe movable contact into engagement with the fixed contact at all times;and it will assure a low resistance engagement between the movable andfixed contacts whenever the handle is in the on position. However, thehigh point on the handle of the switch can overcome the force exerted bythe spring. Hence, the switch that is provided by the present inventionhas a spring which directly biases the movable contact tocircuit'closing' position, and has a handle that provides direct andposi tive circuit-opening movement of the movable contact. Itistherefore. an object of. the present invention to provide aself-containedelectrical switch which has a movable contact in the formof a cantilever plate that is biased toward a fixed contactor by ahelical compression spring, and that can be moved to circuit opening'position by ahandle.

Where electrical switches are small, they can some-- times be subjectedto sufiicient abuse to cause their parts to become separated. from thehousing. If those parts are electrically alive, considerable danger canresult, since the parts may. cause arcing and sparking. The present.invention oviates any such danger-by providing a method of mounting theparts of the switch Which-'- positively prevents accidental separationof those parts from. the housing. Specifically, the housing of theswitch provided by the present invention, hasformed guides into whichthe electrically alive parts extend; and it has openingsthrough whichthe binding screws extend. Those openings are adjacent the closed end ofthe housing, andthey will coactwith that closed end andwitlr theformed"guides of the housing to prevent accidental separation of theelectrically alive parts of the switch after those screws have seatedin. those parts. In this way, the switch can be assembled at thefactory; and" it will be resistant: to the. loss or. separation of anyof its parts. Only. by removing. the binding screws can electricallyalive. parts he removed; and those partswill not be" alive? when thebinding screws are removed; Inthis way, the present invention positivelyprevents thefree ing of. electrically alive parts ofthe switch.

Otherand further objectsand advantages of theiprese'nt inventionshouldbecome: apparent from an-examination of. the drawing and'accompanying description.

In the; drawing andv accompanying description a pre--- ferred embodimentof the present invention has been shQWQanddescribed-but it is to beunderstood that thedrawing and accompanying description are. for the purPOse of illustrationonly and do not limitthe invention nd hat. the.invention will be: defined by the appended claims.

. In the drawing;

Big. 1- is; a. perspective. view of an electrical switch hat is made in.accordance with the principles and teach ings: of; the. present:vinvention,

Fig. Zis. a. longitudinal section of the switch shown in Fig, 15,, andit, is. taken along thenplane defined bythe Fig.- 3. is; anotherlongitudinal section of the switclrof Fig.1 and itis taken along,theplane defined by theline 2.-2;in Fig. 1', and-itshows theswitch-inopen-position;

Big, 4; is another longitudinal section of" the switclr ofiliig.1Lauditistakenalong the plane -defined'by-the I r .3 line 22 inFi'g.- I,and it shows the component parts of the switch in dead center position,

Fig. 5 is a sectional plan-view of the switch of Figs. l 4, and it istaken along the plane defined by the line 55 in Fig. 2, Fig. 6 is an endview of the handle of the switchof Figs. 1-5,

n Fig. 7 is a perspective view of one of the terminals of the switch ofFigs. 1-5,

. Fig. 8 is a perspective view of a J-shaped element used in the switchof Figs. 15, and.

,Fig. 9 is aperspective view of another terminal for the switchof Figs.1-5.

} Referring to the drawing in detail, the numeral 10 generally denotes ahousing of insulating material. This housing will preferably bemolded inone piece, but it can be fabricated if desired. The housing 10 has twovertically directed guiding projections 12 that are-spaced from theright handend wall of the housing 10 to define vertically directedrecesses 14. Two vertically directed guiding projections 16 are spacedfrom the left hand end wall of the housing 10 to define two verticallydirected recesses 18. The vertically directed guiding projections 12 and16 extend all the way from the bottom of the housing 10 to the top ofthe housing, and thus the verticallydirected recesses 14 and 18 alsoextend from the bottom of the housing 10 to the top of that housing. Asa result, the housing 10 coacts with the vertically directed guidingprojections 12 and 16 to define a large central recess and four smallerrecesses at the corners of the housing 10.

. A generally U-shaped shallow recess 20 is formed in the left hand endof the housing 10, and it is formed in the exterior face of thathousing. An opening 22 extends through the left hand end wall of thehousing 10 adjacent the upper end of the recess 20; and that openingcommunicates with the large central recess defined by the housing 10. Agenerally U-shaped recess 24 is formed in the right hand end wall of thehousing 10 and it is formed at the outer face of that end wall. Therecess 24 is closely comparable to the recess 20. An opening 26, whichis closely comparable to the opening 22, extends through the right handend wall of the housing 10 and communicates with the large recess at theinterior of the housing 10. The openings 22 and 26 are in register with,and in alignment with, each other.

A frusto-conical projection or stud 28 is formed on the bottom of thehousing 10 and it projects vertically upwardly into the central recessdefined by that housing. This projectionor stud is in register with theopenings 22 and 26 in theleft hand and right hand walls of the housing10. a

'A pair of notches 30 are provided in the longitudinally extending sidewalls of the housing 10. These notches are in register with each otherand are located approximately midway of the length of the housing 10.These notches are preferably U-shaped in configuration.

Ihe numeral 32 denotes a plate of metal with a tab on the upper endthereof. The plate 32 is dimensioned so .it fits snugly within thevertically-directed recesses 14 in the housing 10. The tab on the upperend of the plate 32 extends horizontally inwardly from the right handend wall of the housing 10. An opening 34 is punched in the plate 32 andthat opening is threaded to receive a binding screw 38. The plate 32carries a contactor 36 on the tab thereof. This contactor coacts withthe plate 32 to define a stationary contact and a stationary terminalfor the switch of the present invention. The contactor 36 willpreferably be made of a material which is resistant to arcing, and itwill be made in the form of a disc with a central projection. Thecentral projection will be extended upwardly through an opening in thetab on the plate 32 and will then be riveted over to hold it fixedly inassembled relation with the plate 32. -The shank of the binding screw 38is threaded and will extend-into and be held by the threaded opening 34.

The head of the binding screw 38 is smaller than the recess 24 in theright hand end of the housing 10.

A short plate 39 of insulation is telescoped between the right hand endwall of the housing 10 and the vertically directed guiding projections12. Thus, that plate will be held in the recesses 14 and will extendfrom the upper end of the plate 32 to the upper end of the housing 10.

The numeral 40 denotes a plate of metal which has a generallyrectangular opening 42 through it. That plate also has an opening 44punched through it and the opening 44 is threaded. A notch 46 isprovided in the hottom of the plate'40 and that notch is spaced inwardlya short distance from each side of that plate. The plate 40 isdimensioned to fit into the recesses 18 defined by the left hand endwall of the housing 10 and the vertically directed projections 16. Thereis some looseness and play between the walls of the recesses 18 and theplate 40.

The numeral 48 denotes a J-shaped strip of flexible metal. That strip ofmetal has an opening 50 punched through it in the closed end of the J;and that opening will be slightly larger in diameter thanis the opening44 of the plate 40. A contactor 52 is fixedly secured to the long arm ofthe J-shaped strip 48 and that contactor will be made of anarc-resistant metal and will be suitably riveted to that long arm of theJ-shaped strip 48. The numeral 54 denotes a binding screw and the shankof the screw can extend freely through the opening 50 of J-shaped strip48 and seat in the threaded opening 44 of the plate 40. The head of thebinding screw 54 is smaller than the recess 20 in the left hand end ofthe housing 10.

As pointed out particularly in Figs. 25, the J-shaped strip 48 is setagainst the left hand face of the plate 40 and the long arm of theJ-shaped strip 48 extends through the opening 42 in the plate 40.Simultaneously, the short arm of the J-shaped strip 48 extends into andis confined by the notch 46 at the bottom of the plate 40. At such time,the. opening 50 in the J-shaped strip 48 is in register with thethreaded opening 44 on the plate 40. Consequently, the shank of thebinding screw 54 can pass freely through the opening 50 and seat in thethreaded opening 44 and thus secure the J-shaped strip 48 to the plate40. At such time the long arm of the J-shaped strip 48 will extendtoward the right hand end of the central recess defined by the housing10. That long arm of the J-shaped strip 48 will be above and out ofengagement with the top of the stud or projection 28. Also, thecontactor 52 on the long arm of the J-shaped strip 48 will be below anddirectly in register with the contactor 36 on the tab ofthe plate 32.The long arm of the J-shaped strip 48 will normally hold the contactor52 in engagement with the contactor 36, but that arm can bend downwardlyto permit the contactors 52 and 36 to separate.

A strip of insulating material 55 in the form of a plate is disposedwithin the upper reaches of the recesses 18. That plate of insulationwill extend from the upper end of the plate 40 to the upper end of thehousing 10.

A helical spring 56 is mounted concentrically with the stud orprojection 28, and that stud or projection will confine the spring 56 tothe approximate center of the recess defined by the housing 10. Thespring 56 will bear against the under side of the long arm of the J-shaped strip 48, and will urge that arm upwardly. Such upward movementof the long arm of the J-shaped strip 48 will normally hold thecontactor 52 in engagehelical spring 56 has an axis which extendsupwardly in a direction parallel to the axis of the stud or projection28. The axis or the stud extends thropgh a line defi ned by the notchesin the housinglql A handle 58 is: provided for the switch of the presentinvention, and that handle has a high "point 59thereon; When the handle'58 is in the fonfi position shown in Fig. 2, the high point 5-9 is.either out of engagement with the long arm .of the J-shaped strip 48 oris loosely resting against that long arm. However, rotationof the handle58 in a clockwise direction will-bring the high point59. almostimmediately into engagement with the long arm of the J-shaped strip 48.That high point will then be moved to the dead center position shown inFig. 4 and at that time the long arm of the J-shaped strip 48 will havebeen bent downwardly to move the contactors 52 and 36 apart. Continuedrotation .ofthe handle 58 in a clockwise direction will move the highpoint 59 to its final off position as. shown in Fig. 3;; and at suchtime the contactors .52 and 36 will be held apart.

The high point 59 is formed by -two intersecting plane surfaces on thehandle 58. "Those plane snrfaces'are set so. one of them isclosely-parallel to the long arm of the J-shaped strip 48 when'theswitch is in the on position, as shown in Big, 2, and so' theother planesurface is closely parallel to the. long arm of the- J-shaped strip 48when the. switch is in the oil position, as shown in Fig. 3. Thisangular relationshipbetween the plane surfaces that define. the highpoint 59 is verydesirable because it enables the spring-applied iorceson the long arm of the Jeshaped strip, 48. to tend to hold the. handle58 in the off position as well as the on position. As-a result,accidental movement. ofthe handle 58 to either of its two positions isresisted. l

The handle. 58 is. provided withv oppositely disposed; trnnnionsdfl.Thosetrunnions are generallycyliridrical in configuration but. theyhave. a conical. or filleted section which merges smoothly withthebodyof the handle 58. The cylindrical portions of the trunnions 60extendinto and: are confined and supported by the notches 30 inthelongitudinally..extendingside walls of the housing 1 The runnions 6,0interact. with the notches 30 to permit guided and: regulated rotationof the handle 58 relative to the housing 10.

A sheet 6 2 of fish paper is provided that overlies the upper. end ofthe housing 10. This fish. paper has an p i g fiil pll h t receive the.handle.58. Thisfish paper will also overlie the upper end of theinsulating Maori? and .5.. i

A cover plate 64, preferably of metal, is provided for the housing 10.That cover Plate. has an opening 66xto receive the handle 58. Theopening 66 is in register with the opening 63 in the sheet62 of fishpaper. The cover plate .4 has cars 68. that can be bent downwardlyover pie ti n t he o pos te e ds of' he housing The bending: of the ears 68,over, those projections will fixedly.- secnre the coverplate 64 to hehOLl ing 10. During the assembling of the coverplate 6 4 with thehousing 10, the cover plate will press; the fish. paperand theinsulating plates and 5 5 downwardly to confine and hold the plates 3;and 4t} .inregister with the. Openings, 22 and 26 in the opposite ends of th e housing ll). Thecoverplate 6 4 also hasthreaded openings 70 whichcanreceive h to a suitable mounting screws that will ho ld-g the ed-set.n1.,.p o the 1 2s Once the cover plate 64ha s-been secured to thehousing 10, the binding screws 3 8and54 can be telescoped'into thethreaded openi s .34 and 44; respectively. During the assembly of plates3; and,4! );-witl1 thehousing 1Q,

those binding screwshad to-beremoved. Once they have been telescopedinto the threaded openings 34 and 44 of the plates and 4t), thosebinding. screws will positively prevent accidental separation oi theplates 3 2 and 40 from the housing-@104 The bindi n-gscrew-'54 will-alsoprevent separation of the d shaped lever 4 firomthe housing It) aslongas its shank is seated in the ,ihreaded opening 44 of the plate 40.

T in e a ti n be ween. .11 2 limit 8. 2 .4511

and the 'plate s 32 and 40 is'very important preveptipg the separationof live parts of the switchfrq p. th h us n .19.- throu rpm; unexpected.a ar-len t qre 'nl t 64 ve so .l.@ b ok n. and. w r to b e se a ate theh using. 1 o e of h ri ajlly ve Pa rs. Qu1d. i t ha s t h housing. Th sis of great'importance since it minimizes the risk of electrical shockand of electrical fires. Specifically, if the cover plate 64 were tobecome separated r m t h si g '10, he h ndl 8- 901 14 a l' y t a n thehousing 10, "the sheet 6 2 offish paper could fall away from the housingand the plates39 'an d 55 of insulation might fall away frornthathonsing. However, the metal plates 52- and 40 and the 'd-shapedstrip 48 could not fallaway from the housing .9 the binding screws 38and 54 positively preventing any such action.

In; the. 9n pos i tion"shown ii Fig. 2 the spring 56 is holding themovable contact in engagement with thefixed contact and the high point59 is at the right hand Side of the'dea dp ce tefpdsit-ion shown in Fig4. I11 the oll position sho'wniin Fig. 3, the movable contact is spaceda predetermined distaneefrom the fixed contact; and the high point 59 ofthe handle 58 is at the lefthand side of the-'dead center positionshown'by Fig, 4. In the dead center position shown in Fig. 4, themovable contact is spaced from-the fined contacta; distance closelysimilar to the distance those contacts are spaced apart in the oposition shownin- Fig. 3-, andthe high point 59 is-in thedead-centerposition-. Thef actthat-the spacingbetween the movable andfixed' contactsin dead "center position is closely similar to thespacingbetween those contacts in- 0 position isimportant sinceits-prevents prolonged-arcing due to the movementof the handle intoadeadcenter position where the fixed and'movable con tacts were closely.adjacent each other.'

It will be noted that the handle 58 drives the movable andfixed:contacts. aparti as it. rotatesfrom on position to off positionand thatthe spring: 56 drives the fixed and moyablecontacts into engagement witheach other as .thehandlemoves; in the opposite direction. Hence,thetpresent. switch gives a positive opening action and a spring-biasedclosing action. The result is that the switch provides a relativelyslowcircuit-breakingoperation because. the handle is-havin-gto opposethe strong helical spring'56 whileit will provide a quick circuit makingoperation because that spring. is then assisting the operatorinirotating' the handle t'o. on po sition The relatively slowv circuitbreaking operation 'isdesirable because it allowsthe. voltageofz'thealternating electrical current to fallatoward the zerovalue and thusminimize arcing.

Itwill be notedthattl e high point 59 on the handle 58 isalwaysrelatively close tothe. dead center-positionshown in Fig. 4. This isdesirable because it reduces the bending IQ QGQES that would .OELCU! ifthe high point 59 were spaced av considerable distance. from that deadcenter position.

Thosebending. moments..-w.ould .not-onlybe in the handle Sig-but wouldalso be in the..longarm ofthe J -shaped' it occupiesan otherwise emptyportion of the recess within the housing-10. This is desirable since itmakes -unnecessary the provision ofa springy metal in the J-shaped-strip 48. -That .l-shaped strip will have some natural resiliencend svshresili nce i he pb s the contacts toward each other but theprincipal circuit making ciae l e. in, l1sfsmin i 1 di us e.

shap edlfstrip 48 car1 b6 3 deoi a large. numberof metals the h n. usfsp n yme ls.

Wh r a a erred mbodiment h P e en nbee-wh m. d dessribedi dbe und r t Wl ing. k lled. in, the-art l ???.Yfipllitha l gssmay: be

7 made in the form of the invention, without affecting the scopethereof,

What I claim is:

1. A manually operable electric switch that comprises a fixed contactor,a movable contactor that is movable relative to said fixed contactor, ahelical compression spring, a handle that is selectively movable to onposition and off position, a terminal that is secured to the said fixedcontactor and is connectible to an electric circuit, a second terminalthat is connected to said movable contactor and that is connectible tosaid electric circuit, said spring being intermediate and closelyadjacent said terminals, said spring biasing said movable contactortoward said fixed contactor but being yieldable to permit said movablecontactor to move away from said fixed contactor, said handle beingmovable to said off position to move said movable contactor away fromsaidpfixed contactor, a pivot for said handle, and a stud that isintermediate said terminals and that extends into and confines. saidspring and holds said spring out of shorting engagement with saidterminals, said stud holding saidspring so the axis of said springextends toward said handle.

2. An electric switch that comprises a housing of insulating material,said housing having a closed side and an oppositely disposed open side,a plurality of contacts, grooves in said housing that extend from saidopen side to said closed side and that guide said contacts, said groovespermitting ready endwise movement of said contacts but preventingsideways or rotative movement of said contacts, and openings in saidhousing and in said contacts to receive binding screws, said openings insaid housing being adjacent and contiguous withsaid closed side, saidbindingscrews extending through said openings in said housing to seat insaid openings in said contacts, said binding screws substantiallypreventing said endwise movement of said contacts and thereby coactingwith said grooves and with said openings in said housing to preventaccidental sepa ration of said contacts from said housing.

3. An electric switch that comprises a housing of insulating materialhaving a closed side and an oppositely disposed open side, a pluralityof contacts, grooves in said housing that extend from said open side tosaid closed side and that guide said contacts, said grooves permittingready endwise movement of said contacts but preventing sideways orrotative movement of said contacts, and openings in said housing and insaid contacts to receive binding screws, said binding screws extendingthrough said openings in said housing to seat in said openings in saidcontacts, said binding screws substantially preventing said endwisemovement of said contacts and thereby coacting with said grooves andwith said openings in said housing to prevent accidental separation ofsaid contacts from said housing.

4. A manually operable electric switch that comprises a fixed contactor,a movable contactor that is movable relative to said fixed contactor, ahelical compression spring, a handle that is selectively movable to onposition and off position, a terminal that is secured to the said fixedcontactor and is connectible to an electric circuit, a second terminalthat is connected to said movable contactor by an elongated strip offlexible metal, said second contactor being connectible to said electriccircuit, said spring being intermediate and closely adjacent saidterminals, said spring acting upon a portion of said elongated strip tobias said movable contactor toward said fixed contactor but beingyieldable to permit said movable contactor to move away from said fixedcontactor, said portion of said elongated strip being substantiallystraight, said handle being movable to said oflf position to move saidmovable contactor away from said fixed contactor, a pivot for saidhandle, and a stud that is intermediate said terminals and that extendsinto and confines said spring and holds said spring out of shortingengagements with said terminals, saidstud holding said spring so theaxis of said spring extends toward said handle, said substantiallystraight portion of said elongated strip enabling said spring to besubstantially free of forces tending to produce sideways deformation ofsaid spring as said handle is moved.

5. A housing having integral sides, bottom and ends, a flexibleconductor that is substantially J-shaped in side elevation, the shortleg and the closed end of said J-shaped conductor abutting,respectively, one end of said bottom and one of the ends of saidhousing, the long leg of said J-shaped conductor extending in agenerally horizontal direction from said one end of said housing towardsaid opposite end of said housing, an L-shaped conductor in sideelevation, said L-shaped conductor having the long leg thereof abuttingsaid opposite end of said housing and extending upwardly from saidbottom and having the short leg thereof extending from said opposite endof said housing toward said one end of said housing in a generallyhorizontal direction, said short leg of said L-shaped conductoroverlying the free end of said long leg of said J-shaped conductor, acover, and a handle that has a finger-receiving portion projectingoutwardly from said cover and has a conductor-engaging portionunderlying said cover and engageable with said long leg of said J-shapedconductor.

6. A housing having integral sides, bottom and ends, a flexibleconductor that is substantially J -shaped in side elevation, the shortleg and the closed end of said J-shaped conductor abutting,respectively, one end of said bottom and one of the ends of saidhousing, the long leg of said J-shaped conductor extending in agenerally horizontal direction from said one end of said housing towardsaid opposite end of said housing, an L-shaped conductor in sideelevation, said L-shaped conductor having the long leg thereof abuttingsaid opposite end of said housing and extending upwardly from saidbottom and having the short leg thereof extending from said opposite endof said housing toward said one end of said housing in a generallyhorizontal direction, said short leg of said L-shaped conductoroverlying the free end of said long leg of said J- shaped conductor, aspring which biases said long leg of said J-shaped conductor toward saidshort leg of said L- shaped conductor, a cover, and a handle that has afingerreceiving portion projecting outwardly from said cover and has aconductor-engaging portion underlying said cover and engageable withsaid long leg of said J-shaped conductor.

7. A housing having integral sides, bottom and ends, a flexibleconductor that is substantially J-shaped in side elevation, the shortleg and the closed end of said J-shaped .conductor abutting,respectively, one end of said bottom and one of the ends of saidhousing, the long leg of said J-shaped conductor extending in agenerally horizontal direction from said one end of said housing towardsaid opposite end of said housing, an L-shaped conductor in sideelevation, said L-shaped conductor having the long leg thereof abuttingsaid opposite end of said housing and extending upwardly from saidbottom and having the short leg thereof extending from said opposite endof said housing toward said one end of said housing in a generallyhorizontal direction, said short leg of said L-shaped conductoroverlying the free end of said long leg of said J-shaped conductor, aspring which biases said long leg of said J- shaped conductor towardsaid short leg of said L-shaped conductor, a cover, and a handle thathas a finger-receiving portion projecting outwardly from said cover andhas a conductor-engaging portion underlying said cover and engageablewith said long leg of said J-shaped conductor, said conductor-engagingportion of said handle overcoming the bias due to said spring when saidfinger-receiving portion of said handle is in a predetermined position.

References Cited in the file of this patent UNITED STATES PATENTS1,470,776 Stevenson Oct. 16, 1923 (Other references on following page) 9UNITED STATES PATENTS Graham et a1 May 28, 1935 Thirlwell Aug. 18, 1942Hutt Nov. 9, 1943 Gaynor May 17, 1949 Chrastina Nov. 21, 1950 Minch'eta1 Jan. 16, 1951 Russell et a1 Oct. 9, 1951 Shewnon et a1 June 21, 1955Great Britain Jan. 17, 1951

